1. Field of the Invention
The present invention relates to a storage controller for managing data using such a physical disk as a magnetic disk and method thereof, and more particularly to a RAID controller for managing data with redundancy, and control method thereof.
2. Description of the Related Art
For a storage equipment using such a storage medium as a magnetic disk, magneto-optical disk and optical disk, the format must be written to the storage medium to access the storage medium when requested by the data processing unit. There are two types of formats: a physical format such as the CKD format, and a logical format where a data area is separated in the processing unit of the host OS (e.g. in block units), and is identified.
By such formatting of the storage medium, the storage medium can be accessed (read/written) based on the host commands of the host OS. The physical format is the initialization processing of the medium in track units, and logical formatting is the format processing of the data area of the tracks, where physical formatting has been performed, in block units. Format processing takes time to format all the blocks of the medium, and in actual use of an unformatted medium, a long wait time (e.g. 30 minutes or more) for format processing is required.
To solve this problem, in a prior art, the storage medium is available immediately without performing format processing as the initialization processing, and performing format processing on the target block when a write access request is received, and then write operation is executed on the target block(e.g. Japanese Patent Laid-Open No. H8-147110).
In prior art, the logical formatting is executed when an access request is received, so logical formatting is not executed when the access request is not received. This prior art is suitable when such data as music and images are continuously written to one medium, such as an MD (Mini Disk).
However, when data is accessed randomly, such as the case of a large scale storage system connected to a host and server, both logical format processing and access processing must be executed for each access, so the time required for access processing increases, and access time becomes long.
Particularly in a RAID storage system which manages data with redundancy, the time required for logical format is several tens of minutes to several hours, depending on the size of the logical volume, so the access time increases in order to construct a new storage system and to add a logical volume to a current system.
Also for a RAID system, logical formatting considering the redundancy of data is necessary.